This is anne hathaway's last-minute fashion switch. She looked fantastic in that prada. But cecilia vega reports that may not be the dress she originally picked for the red carpet. Reporter: Call it dressgate 2013. My mom says it's business in front, party in the back. Reporter: Anne hathaway may have walked down the oscars red carpet in pink prada. But she had reportedly been planning to wear an entirely different dress by an entirely different designer. Just before the awards show started, an excited valentino sent out this announcement saying hathaway would be wearing its pink embroidered tulle illusion gown. The intrigue. I have rumors that this may have been anne's. And it may have looked too much like her "les mis" co-star. Nobody wants their dress compared to someone else's on a big night. Reporter: Hathaway is a valentino loyalist. She's worn the label to countless red carpets. Even to her own wedding. Whether or not an actress wears a designer's dress on the red carpet is a huge deal to the designer. Reporter: This morning, the fashion world is buzzing. Was it a devilish snub to wear, gasp, prada? I think that depends on what you're -- it wasn't a question. Reporter: Hathaway's camp has no comment. But the pixie-haired star told rain seacrest, it was a last-minute decision. I didn't know what I was wearing until about three hours ago. Reporter: Hilary swank is no stranger to the last-minute switch. She reportedly changed her mind before walking the red carpet twice before. And went on to win oscars each time. Proof that just maybe, the oscars' gown switch-a-roo. And the oscar goes to. Reporter: Makes for oscars luck. Miss anne hathaway. Reporter: "Good morning america," cecilia vega, abc news, los angeles.

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